PHILADELPHIA - The question of which sections of New Orleans will be rebuilt - and how - remains capable of raising tempers and furrowing brows, even in Philadelphia, 1,100 miles from Hurricane Katrina's kill zone.

With thousands of urban planners gathered here this week for their annual convention, the issue came up at least twice Sunday, first during a session exploring New Orleans' citizen-driven recovery efforts and again during a talk on the likelihood that global climate change will fuel more catastrophic disasters.

The New Orleans leaders who came to share stories of ravage and rebirth, including City Hall recovery czar Ed Blakely, made no apologies for their plans to revive every neighborhood paralyzed by the flood - and to create an environment in which every displaced resident can return. But they also made it clear that New Orleans is being rebuilt in a strategic way, with the possibility that residents themselves will elect to abandon areas most prone to flooding.

"The way we build is going to be very important," said Blakely, whose recovery work in the wake of earthquakes in Oakland, Calif., and Kobe, Japan, ranks him as a celebrity at the American Planning Association conference. "Stick-building may not be our future. Building on slabs may not be our future. We may have to start looking at building with other materials, including steel."

Blakely's answer did not satisfy everyone in a room packed with professionals still fascinated with New Orleans' fate. A man stepped to the microphone and asked: Why should New Orleanians be allowed to rebuild homes and business in locations where they would "actually be in harm's way in doing so?"

"What we are doing in New Orleans is creating opportunities for people to move out of harm's way by offering them incentives" for relocation from repetitive-flood areas or low-lying areas to safer areas, Blakely replied. "We're going to allow people to switch from a place that might be dangerous to the center of the city - to a place that might be safer for them."

After his speech, however, Blakely acknowledged that the only "incentive" package in place right now is the state's Road Home buyout option, which pays as much as $150,000 to homeowners who want to dispose of their storm-ravaged properties. City Hall, he said, is working on a separate program that could provide financial incentives to residents to settle in "clusters" on high ground in their neighborhoods and around the 17 zones he unveiled this month as places the city will target public spending to spur private investment.

No city program is available yet, though, he said.

Some returning, some new

Probing the recovery issue in more general terms, a participant at another session asked the chief directors of the Unified New Orleans Plan whether it's realistic, based on current population estimates, to believe that all displaced residents will be able to return. A U.S. census survey found that 223,000 people lived in New Orleans in July 2006.

"Yeah, it's realistic," said Stephen Villavaso, who directed the portion of the unified plan that deals with citywide policy initiatives.

City planners often have faced similar questions, typically posed as if the city's future population potential hinges solely on how many of its pre-Katrina residents return. Blakely and others have said that New Orleans' future population will be a combination of its pre-Katrina population and new residents who want to seize opportunities born of the rebuilding effort.

The population potential, Blakely has said, depends on the quality of the rebuilding job and the quality of life the rebuilt city presents to potential residents.

With regard to displaced New Orleanians, Villavaso said Sunday that everyone cast out of the city by Katrina should have the chance to return to the same - or better - neighborhood and quality of life as he or she enjoyed before the August 2005 disaster.

"It's an opportunity for everybody to return," he said of the unified plan's goal. "If somebody makes a decision not to return, that's a decision."

Laurie Johnson, another UNOP director who spoke at the same session as Villavaso, pointed out that New Orleans' geographic "footprint" is large enough to sustain a substantial population, noting that a similarly sized area around San Francisco is home to 1.5 million people. But she, too, pushed "clustering" to protect lives and private property, along with public investments in assets such as schools and police stations that will attract future residents.

"Money has to be put in place to incentivize people to live more safely," she said, and to assure that similar investments in public assets are safe.

Global warming

Blakely also spoke at length about the effects of global warming on populated areas. The topic is a focus for the first time this year at the American Planning Association's yearly meeting, which kicked off Sunday with a lecture by environmental activist Robert F. Kennedy Jr.

New Orleans, Blakely said, "is the first major American city that has been almost totally destroyed by the natural event. This is something we should anticipate happening elsewhere."

Blakely implored planners to be mindful of the regional connection of community development, as well as the importance of such protective natural resources as forests and marshland.

"Unless we rebuild the natural systems, we don't have any hope of surviving the future," he said. "We have to understand that we're global citizens, not just local citizens."

Sunday's two talks on New Orleans each drew more than a hundred participants, demonstrating the continuing interest in the city's plight and the civic lessons implicit in its rebuilding struggle. About a dozen sessions this week are slated to focus on Gulf Coast recovery and disaster-prevention issues.

'I'm from New Orleans'

Meanwhile, Sunday's event marked Blakely's second public appearance since facing criticism for making controversial comments to the news media about New Orleans' population and saying that outsiders interested in aiding the city were unlikely to tolerate local "buffoons." He spoke to reporters Friday in New Orleans, where he stopped for several days after a weeklong visit to Australia, a trip to Washington, D.C., to testify before Congress and the Philadelphia appearance.

Blakely never failed Sunday to refer to himself as a New Orleanian, frequently using the words "we" and "us" to refer to residents' recovery efforts.

"I'm from New Orleans," he said in introducing himself. Blakely began his work as director of the Office of Recovery Management in January and lives in the Garden District. He also maintains a home in Sydney, Australia, and a faculty position at a university there.